1. Field of the Invention
The embodiments described herein are related to inorganic particles such as nanoparticles.
2. Description of the Related Art
Nanoparticles are increasingly finding uses in many applications. Various methods, including thermal plasma synthesis, are available to prepare nanoparticles. One method involves thermal plasma treatment of precursors in a liquid form, such as substantially neat liquids and solutions, introduced into the plasma as droplets. Currently, many believe that when precursor materials are introduced into a plasma as a liquid solution, all materials, both the solutes and liquid components, are completely vaporized in the plasma. After the precursors are vaporized in the plasma, they cool as they begin to pass out of the hotter areas of the plasma. It is believed that when the vapors begin to cool, they become supersaturated and particles start to nucleate, then sometimes agglomerate and/or coagulate. Thus, many currently believe that the size of the particles is a function of the cooling process of the vaporized material, and is not dependent upon any processes that occur before the precursors are vaporized in the plasma. Thus, for example, additives intended to affect the size of droplets introduced into a flame-assisted pyrolysis, such as those described in Purwanto et. al. (J. of Alloys and Compounds 463 (2008) 350-357), would not be expected to affect particle size if used in a plasma process.
Current efforts to control nanoparticle size are directed to quenching processes carried out on the nucleating vapors passing out of the hotter areas of the plasma. According to current models, rapid quenching, on the order of about 50 microseconds, is believed to be required to obtain particles with a diameter of less than 100 nm (see, for example, Leparoux, et. al., Advanced Engineering Materials 2005, 7, No. 5 349-353, esp. FIG. 2). Thus, improved quenching methods are currently being sought to reduce particle size. This application describes a non-quenching based methodology for obtaining nano-sized particles independent of the material system and/or reactor configuration.